1. Technical Field
This invention relates to injection mold tooling and more specifically to efficient installation and removal of mold tools from mold presses.
2. Description of the Prior Art
In a typical molding shop there are several different sizes of mold presses and for each of these different press sizes, there are also many different mold tool sizes. Considerable time and effort is required to install and remove these variously sized mold tools as each generally requires a different method of installation, special alignment and a varying number of and arrangement of fasteners for securing such tool to mounting plates or pressure platens on a mold press.
In an effort to reduce this time consuming and inefficient process, standard quick change plates are now used for a particular family of press sizes. The various size mold tools are all mounted to quick change plates which are one standard size. A more efficient procedure is provided thereby since this essentially makes all tools for use with a particular family of press sizes to be the same from the standpoint of installation and removal of these tools from the mold press.
In a further effort to reduce the time required to remove a mold tool from a mold press and replace it with another, mold press arrangements employing common quick change plates also employ a hydraulic system to quickly secure the quick change plates after insertion of the tool. The hydraulic system also serves to retain the tool in the proper position during a molding operation. Securing of the mold tool is via retention tabs which are activated by the hydraulic system for seating and retaining the mold tool in the proper position.
A possible safety hazard may exist with this arrangement, however, if the retention tabs do not correctly seat the mold tool in place during installation. The mold tool consists of two parts which have complementary mating surfaces and are brought together between two platens with an extremely high contact pressure. Any misalignment of these two parts can result in damage occurring to the mold tool. Moreover, if the hydraulics fail during the normal molding operation, it is possible for the tool to be pulled out of position and fall from the mold press to the surface below. Each of these conditions could cause injury to an operator due to tool fragments being projected from the mold assembly or also molten plastic escaping from this assembly.
A disadvantage generally present in the design of mold press arrangements is that tie bars in the mold press are not adequately protected from damage during mold tool installation and removal. These tie bars provide the bearing surfaces for the moving platen and for alignment of the two platen surfaces. Another disadvantage of the described mold press arrangement is the relatively high cost of the hydraulic system used for securing the quick change plates.